Electric safety-fuse.



R. C. COLE.

ELECTRIC SAFETY FUSE.

APPLICATION FILED APR. 7, 1914.

Patented D80. 29, 1914.

'Izno'rx STATES PATENT oFF1cE nonnn'r c.; comor'nn'nrronn, coNNncrrcUr, assrenon ro 'ma sonnsaarr comm. or rammen, connncrrcnr, a .rorNr-srocx coaroaarroa or connnncrarc SAFETY-rusa.

' speumemon of Letzer; raten.

Patented Deleg-'29, 1914.

To all 'whom z't ma concern.'

Be it known t at I, Ronnar C. Conn, a citizen of the United States, residing at Hartford, in the county of Hartford and State of Connecticut, have inventeda new and useful Improvement in Electric Safety- Fuses, of which the following is a specification.

This invention relates to the construction of a fuse which is particularly adapted for protecting the conductors and apparatus `of telegraph, telephone, signal and simllar circuits, in which the amount of current, used is relatively small.

The object of the invention is to provide a sensitive fuseof small capacity, which, while simple and inexpensive to manufacture, will be ver durable and quite accurate and eilicient in action, and will plainly. indicate when the fusible element has been disrupted and the conductors separated so as to open the circuit. a

-Of the accom anying drawings, Figure 1 shows a centra longitudinal section of a fuse which embodies this invention. Fig. 2 is a view on larger scale showing a portion of the heat-coil ends of the interior tension conductors which are joined by a rivet made of easil fusible metal. Fig. 3 is a similar view o the artsshown in Fig., 2 turned 90. Fig. 4 1s a view of the easily fusible rivet which is used to join the coiled ends of the interior conductors. Fig. 5 is a longitudinal section on enlarged scale of one end of the fuse. Fig. 6 is a view looking atthe end of the fuse. Fig. 7 shows the ends of the conductor heat coils joined by a rlng of low melting point metal. Fig. 8 is a similar view of the parts shown in Fig. 7 turned 90. Fig. 9 shows a view of the easily fusible ring.

The tubular casing 1 of this fuse is made of ber or other suitable insulating material in the usual way and of approved diameter and length. Fitted on each end of this tube is a metallic -ferrule 2. These ferrules, usually made of brass, form the exterior conducting terminals of the fuse land are designed to be engaged with the commonly used clips or contacts to which the terminals of the circuit wires are fastened. The end of each ferrule has a central opening 3 and is desirably made rentrant about the open# ing for the reception of a metal disk 4. Each of these disks is perforated for the passage of the conductor 5 and is slitted so that the conductor,l which has an enlarged end 6, may be slipped into the perforation. The conductors '5 are referably made of German silver wire, alt ough they may bel wires of steel or other metal. The inner end of each conductor has a loop 7 and adjacent to the loop is coiled as at 8. These coils serve as heat coils and at the same time act as spiral springs.

The disks at the ends of the fuse are held 1n place so as to close the openings through the ferrulesA by the pull of the heat-coil sec- 'tions of the conductors. The looped inner ends of the conductors may be joined to or ring is made off an alloy (ii-metal that melts at a very 10W temperature, desirably about 212 F. Links formed of conductors with spring heat-coils, joined by rivets or r1ngs in the manner described can be made in large quantities cheaply and with such uniformity that they can be depended upon to operate Within very closelimits, for the conductors with the spring heat-coils can be made with an absolutely determined electrical and thermal capacity and mechanical pull, and the rivets or rings may be made in large quantities so that every one will have the same strength, conductivity, and degree and time of fusion. Furthermore this method of forming the links insures such a strongand durable connection that there is no liability of mechanical rupture and disconnection of the parts from any cause except that resulting from the heat evolved by the predetermined abnormal rise of current.

The construction described herein is of particular advantage in fuses provided for telegraph lines, such for instance as is thefuse illustrated in the accompanying drawings, wherein the currents used are less than ten amperes, and commonly from one tenth of an ampere to one am ere in quantity. The fuse illustrated is designed to be rated for six tenths of an ampere and to open at eight tenths of an ampere, which means that the rivet or ring must be heatedand fuse so that the conductors will pull a art with an increase of only two tenths o an ampere in the current. The fusible element.:

must, consequently, be made small and of an alloythat 4will fuse every timek at a'low temperature, and yet must be stron and durable so as to withstand the strams of ordinary use and the variations of atmes-v pheric ,1conditions.-A These fuses areeasily and clea ly renewed after being blown. The con uctors joined together as described and put in the tube with the ferrules atthe ends, 4'are en aged with the disks` by bending' vtheA slitte the en ds of-fthe conductors into Athe central perforation@4 and then bending back the disks. The tension of the coiled portions of tlieconductors draws the disks into the reentrant ends of the ferrules 'and holds the parts in place while the link is in;normal.

condition. As these fuses in use are usually arranged vertically, when the-rivet or ring is melted bythe slight excess of the small current, the heat-coil springsv pull the conductors apart, and the'lower conductor with its disk drops down and thus plainly indicate's that the conductor has been disrupted and that the circuit is open. If the fuse is arranged horizontally, the reaction of the springs'as the rivet or ring gives way, tends to `'thrust out the4 disks at both ends.l

-"llhie invention claimed is: l

-1. A fuse consisting of an insulating vcasing,"'meta`llic ferrules at the ends of the casing, conductors with spring heat-coils in the casing and 'having theirouter' ends electri- .cally connected with said ferrules, and a rivet formed of a low melting metallic al loy'connecting the` inner endsgof the con-- ductors.

portions and slipping 2. vA fuse having an insulating casing, metallic ferrules with ervforated rentrant ends ttn the ends of, the casing, metallic disks loose y located 'in 'said' rentrant'lends, conductors within the casing, the-outer ends of the conductors engaging and holding said-disks and `the inner ends of the lconductors being coiled into the formof' spiral springs, and a link of low melting point metallic alloy joining the coiled ends of the conductors. v j

3. A fuse consisting of an insulating cas7 ing, metallic ferrules with openings through e "their ends, set on the Iendsof the casing,

disks on the'exterior oftheopenl ends of the ferrules and closing the openings therethrough, yand main conductors with Itheir mamme ductor between the heat-coils being of low` occupying fusing metal, and disks loosely the openings in the end ferrules and normally held there with a yielding force by the enlarged outer ends of said mainlconductor.

ROBERT C. COLE. Witnesses:

'HAZEL G.BRA1'NARD, DUNCAN C, HOOKER.

inner ends joined by a fusible rivet and" 

